Magnetic recording and reproducing device with means to prevent accidental erase of record medium



Aprll 5, 1949. VAGTBQRG 2,466,514

MAGNETIC RECORDING AND REPRODUCING DEvICE WITH MEANS TO PREVENTACCIDENTAL ERASE OF RECORD MEDIUM Filed Nov. 23, 1944 M 5 Sheets-Sheet lMAGNETIC RECORDING AND REPRODUCING DEVICE WITH MEANS TO PREVENTACCIDENTAL ERASE April 5, 1949. H. A. VAGTBORG 2,466,514

OF RECORD MEDIUM Filed Nov. 25, 1944 v s Sheets-Sheet 2 Aprnl 5, 1949.H. A. VAGTBORG 2,466,514

MAGNETIC RECORDING AND REPRODUCING DEVICE WITH MEANS TO PREVENTACCIDENTAL ERASE I OF RECORD MEDIUM Filed Nov. 23, 1944 3 Sheets-Sheet 3I V l Patented Apr. 5, 1949 MAGNETIC RECORDING ANDREPRODUCIN G DEVICEWITH MEANS TO PREVENT ACCI- DENTAL ERASE'OF RECORD .MEDIUM Harold A.Vagtborg, Chicago, 111., assign'or to Armour Research Foundation ofIllinois Institute of Technology, a corporation of Illinois IApplicationNov-ember 23, 1944, Serial-No. 564,824;

3 Claims.

This invention relates toamagnetic recording and reproducing device andmore. articularly to a magnetic recorder of "either the magazine loadingtype or the spool loading type, in which safety means: is provided toprevent erasing: or injury to professionally recorded records or otherrecords. of a permanent nature.

One of the principal features and objects of the presentiIIVBI'ItlOIIIiS tO provide anovel magnetic recording and reproducing'device of the magazine loading type in which means is pro:- vided todistinguish between magazines having a record thereinof apermanentnature andmagazineshaving arecordathereinor a blank wireupon whichrecordings may bemade and then removed.

Another object of the-present invention is to provide a novel magazinefor holding a magnetizable medium.

.A further object of thein-ventionis to provide novelin.terlocking.:means. between the recording circuit of a magneticrecorder .andpthe magazine.

Another and still furtherobiectof the present invention is 'to. providenovel means "for selectivelydistinguishing between wire carrying spoolswherein with spools of one typeinterlocki-ng means is provided whichwill preventtheerasing head of the magnetic recorderirom. beingenergized and. which will preventany new recording being made on thewire o'f the. magnetic 're.cord in-g device.

Still another and further objectv of th'e'present invention is to:provide 'a novelumagne'tizable medium carrying device and mountingtherefor.

The novel features which IIbelie-ve to bexcharacteristic of my inventionare set forth with particularity-in the appended claims. My inventionitself; however, both as to its manner z'ofv construction and method ofoperation, together with further-objects and advantages thereof, maybest be understood by reference to the following description; taken inconnection with the a'ccom panying drawings, in which:

Figure 1 is a schematic wiring diagram of 'a magnetic recording andreproducing device;

Figure 2 is an isometric view of a wire magazine which may be usedwith amagnetic recording and reproducing device of the type schematicallyshown in Figure v1.;

Figure 3 is an end viewof a wire magazine in place on the deck or panelof a magnetic recording and reproducing device with-thedeck. or panelshown in section;

Figure 4-is an-end view similar toFigure 3 but showing a magazinesimilar to the "magazineof '2 Figures 2 and 3 but in which a variationof the safety device is provided; I

Figures 5 and. 6.. illustrate a modified 'form of the present inventionwherein wire spoolsor-reels are employed outside of a magazine, andwherein with certain spools (Figure 6) areprovided safety means toprevent undesired demagnetization;

Figure 7 is a switch of the type employed in the mechanism shown inFigures 5. and 6 with its-cover removed;

Figures 8 and 9. are variations of the second embodiment of theinvention shown in Figures 5 and 6 but wherein the spools having a,permanent recording thereon arev provided with an annular groove on therear face instead of. an annular rib; and I Figures 10 and 11 are viewsillustrating a third embodiment of the. present invention showing wirespools. or reels-mounted on the panel of a magnetic recording device.

Referring now to the first embodiment of the present invention.illustrated in Figures 1 to 4 of the drawings, I have shown, in Figure1, 'a schematic wiring diagram of a magnetic recording and reproducingdevice. More particularly, the magnetic recording and reproducing deviceincludes a magnetic recorder head l0 which is in the general shape of aU having-inturned confronting polar portions II and. I2. This coremember of the magnetic 'head is provided with a magnetizing winding l3which operates both as-a magnetizing coil and as a pick-up coil,.depending upon whether the device. is being used to make a recording onor receivev a transcription from the magnetizable medium 14. Thismagnetizable medium I4 is preferably in the form of a steel wire suchfor example as a medium carbon or a stainless steel wire ofapproximately .004 inches in diameter.

The electrical circuit with which the magnetizing head H3 is connectedincludes a stage I 5 of preamplification which is used to giveadditional amplification of a microphone pickup when a microphone isbeing used, and is also used for additional amplification when thedevice is being used as a reproducer. It also includes a conventionalaudio-amplifier I 6 which may be of any suitable design. Thisaudio-amplifier I6 is connected to, the pie-amplification stage l5 andalso to a jack 11 through which the circuit may be connected to a radioreceiver. Suitable biasing potentials and power for thepre-amplificati'on stage and amplifienas well. as for other portions ofthe circuit presently to be described, are obtained from a power pack orpower rectifier gen erally designated by the reference character I8.This power rectifier may be of any of the conventional transformerrectifier tube types, and is arranged to receive energy from analternating current source through a plug IS. A switch 20- is alsopreferably provided in this circuit to provide convenient switching forthe power pack.

When the magnetic head I is being used as a recording device, arelatively high-frequency alternating current is preferably supplied tothe coil |'3 in addition to the audio wave supplied from the amplifierHi. This provides an alternating current bias for the head which givesparticularly good results. This high-frequency current is obtained froman oscillator 2| which is connected to the input circuti of the magnetichead In through a coupling condenser 22. The oscillator is also used tosupply energy to the erasing head 23 which is in the form of a coilsurrounding, or in close proximity to the wire Hi.

The output of the audio-amplifier I6 is connected through a couplingcondenser 24 to a filter equalizer circuit 25 and then into the inputcircuit of the magnetic head through the conductor 26. The audioamplifier I6 is also connected to a loud speaker 21. As will now beexplained, the magnetic head is arranged to be con nected to the inputof the pre-amplifier stage l and thence through the amplifier IE to theloud speaker 21 when it is desired to reproduce what is already recordedon the wire l4. When the magnetic head I0 is being used to make amagnetic recording on the wire [4 it is connected to the oscillator 2|through the coupling condenser 22 and also to the output of theamplifier I6 through the equalizer network or filter 25. In order toaccomplish this, suitable switches are provided, as is illustrated inFigure 1. More particularly, the input of the pre-amplifier stage I5 isconnected through a switch 28, a conductor 29 and a switch 38 to oneside of the coil l3 of the magnetic head Ill. The switches 28 and 30 areof the single pole double throw type. The conductor 29 is preferablyshielded as at 3|, the shield being grounded as at 32. When the switch30 is moved from its full line position to its dotted line position, asshown in Figure 1, the conductor 29 is grounded. When the switch 28 ismoved from its full line position to its dotted line position, thepre-amplifier is connected to a conductor 33 which extends through aswitch unit 34 to a microphone terminal switch 35. A switch 38 isprovided in the conductor 26 in such a manner as to reverse the end ofthe coil l3 to which the conductor 26 is connected. It will be notedthat the right-hand end of the coil I3 is grounded as at 31'. A switch31 is provided for shorting out the equalizer network or filter when thedevice is being used as a reproducer. Switches 38 and 39 are alsoprovided in the circuit leading to the radio receiver jack H and in thepower supply circuit to the oscillator, respectively.

While it has not been specifically shown, it will be understood thatsuitable means is provided to move the wire l4 and this preferably isenergized from the same power source as the power pack l8.

The above description of a typical magnetic recording and reproducingdevice is believed sufficient for a full understanding of the novelteachings of the present invention. The physical structure of the abovedescribed recording and reproducing device will not be specificallyillustrated except to indicate the manner in which the wire is handled.In the preferred embodiments of the present invention the magneticrecording and reproducing device is equipped with a magazine such, forexample, as the magazine 40 shown in Figure 2. This magazine 40 containsa pair of spools or reels 4| and 42 upon which the wire I4 is mounted.These spools or reels 4| and 42 are mounted on shafts 43 and 44respectively. The ends of each of these shafts 43 and 44 are providedwith pins 45 and 46 to provide a positive clutch engagement withsuitable driving spindles (not shown) which are arranged in the machineto cause rotation of the spools.

The magnetic head i0 is contained within the magazine 40 and it issuflicient for an understanding of this invention to know that when themagazine is dropped into place in the machine and the recording unit isenergized, the spools are rotated to cause relative movement of the wireM with respect to the head It). Figure 3 illustrates the magazine 4|!disposed in place in a cradle or pocket 41 mounted in the upper deck orpanel 48 of a magnetic recording and reproducing device. Mounted belowthe pocket 41 are the three switch units 34, 38 and 38 whichhave beendescribed in Figure l.

The magnetic recording and reproducing device diagrammaticallyrepresented in Figure 1 is of such character that it may be used to makenew magnetic records on the wire I4 or it may be used to reproduce therecording which is already on the wire l4. In actual use there will beoccasions when the wire |4 contains a recording which it is undesirableto erase either intentionally or accidentally. Such recordings might bethose of a symphony impressed upon the wire by a professional recordingcompany, or might be a record of events which should be preserved. Whenrecords of this character are being used in the machine, it would beextremely unfortunate if the switches were accidently thrown to aposition where the erasing head 23 is energized or where the coil I3 isconnected to the output of the amplifier l6. There are other occasionswhere a recording may have been made On the wire I from an incomingradio program through the Jack I! or through the microphone connection35, which is of a temportary nature. In order to re-use the wire theequipment must be of such a character as to enable demagnetization ofthe wire and rerecording thereon.

One of the principal features of the present invention is to providemagazines for these difierent above uses which are similar in everycharacter with the single exception of a special safety device which isassociated with the records of a permanent nature and which will preventthe oscillator 2| from being energized. Such an arrangement is shown inFigures 2 and 3 of the drawings, wherein the magazine 40 is providedwith a projecting pin 49 on the under surface thereof. When thismagazine is dropped into place in the pocket 41, the pin 48 projectsdown through the opening 50 and engages the end of an actuating rod 5|to which the bridging contacts 52 of the switches 34, 38 and 39 areconnected. This causes the bridging contacts to snap to their uppermostpositions and thus causes disengagement of the stationary contacts 53and 54 of each of the switches 34, 38 and 38. A switch of the typeherein illustrated is of the over-center snap-action type. Theseswitches are of such acharacter that downward movement of the stem 5|causes anupward snapping of the bridging members 52, while upwardmovement1.:of- -.thestem .1 l' causes the xbridgingzmem bers tomsnapato:their lower apositionsiin .engagement with the stationary contacts :53:and. 54. These switches 34, 38tandr39, =with't-heir bridging-contacts.52 inthe upper'pgosition are in:an:.unstab1e :position, andzuponrelease of the pressure on the .upper endzof' the .stem '51 the bridgingcontacts 52' will snap back to their lowerpositions.

'- "From the :above: description 1 it will be apparent that when avmagazine having a projecting pinv laisthereon is dropped into place theswitches 34, 381 and '39 :are open. This prevents operation of the.device as a recorder and also prevents energization of the erasinghead. The same general type ofmagazine, but nothaving -a pin 49"thereon, dropped into place, will not cause opening of the switches 34,38 and =39-and' the device may then be used either as a recorder orreproducer, depending upon how the otherswitches in the circuit arethrown.

-A variation of the: foregoing device is illustrated in Figure 4 of thedrawings. More particularly, the microswitches 34, 38 and 39 are soarranged that the upper contacts 55"and 56 are the ones which areconnected into the electric circuit, and the lower contacts 53 and Marcdummies. It will thus be understoodthat when the stem'member 5| carryingthe bridging contacts 52 is in itsupper position, all of the switches.34, '38 and 39are open, while when the stem member 5| is depresseddownwardly the switches 34, 38 and 39 are closed. In this typeof'arrangee ment, a magazine 5-7 is provided having a recessed portion58 therein when it isbeing usedto house wire having a permanentrecording thereon. When such a magazine is employed, the insertion ofthe magazine 5! into the-pocket 41 will not effect actuation of thenormally open switches 34, 38 and 39,, and the device cannot, therefore,be used'to record, nor will the erasing. head 23 .be energized. When amagazine is inserted, however, having a perfectly fiat base wall,v thebase wall will .engage the end of the stem member 5| and cause closingof the switches 34, 38 and-39.

Asecond embodiment. of the present invention is illustrated in Figures5, 6' and 7 of the drawings. More. particularly, in this embodiment ofthe invention the wire i4 .is mounted on at'akeofi spool 59 which iscarried on the shaft 60. The shaft 60 extends through a bushing 6| inthe front panel 82 of the magnetic recording and reproducing device (notshown). The switches 34, 38 and 38 are mounted as a gang switch, onlythe front switch 34 of the gang being shown. These switches are of atype similar to those described in connection with Figure 3 of thedrawings. Each includes a stationary contact 63 and a stationary contact64 which are bridged by a bridging contact 65 carried on a pin 66 whichis mounted for limited longitudinal movement. A leaf spring 6'! isconnected at an intermediate point to the pin 66 and is engaged at oneend by a notch 68 in the housing 69 of the switch. It is engaged at itsother end by a v-shaped member which is securely mounted on a shaft 1!which is arranged for limited rotational movement. The distance from theshaft H to the notch 68 is slightly less than the length of the spring61 so that the Spring 67 is arranged to stop between two positions. Astop member 12 is provided which limits the downward movement of thespring 61. This spring 6! differs from the arrangementsshown in Figure.33; in -that it has 'tworstable positions; one position beingwith the"bridging contact in. -.engag.ementwith the stationary contacts 63 and64 and the other position being with the bridging contact 65::inanopenposition and thespring-(i! in engagement with thestop 7.2. This isimportant "for a; reasonwhich will presently be apparent.

A crankarmor link 13 is rigidly secured to the end of the shaft 1! whichproiectsoutof' the switch housing E59. This arm 13 is slotted asat'14 toseize a pin 15 carried 'on' a follower member -16. It will also .beunderstood that the. shaft 'l'i proiec'tsthrough all of the'switch casingsandthus actuates three switches which are the three switchesdiagrammatically represented, as '34, 38 and 38 in Figure lot thedrawings; The sha'ft H also carries an L-shaped finger 'fl which:projects through an opening I8 in the front panel 6201 the instrument.When the shaft LI is in theposition asshown in Figure- 5 of' thedrawings, the switches 34, 38' and 39 are closed. When an ordinary spoolor reel 53"ismounted on' the shaft 6| the reel 58 does not contact thefollower member I6 'and'the switches: 34, 38 and 39 remain in theirclosed position. If,=on the other hand, -a reel 19 is-provided which issimilarin every character to the reel 59 with the exception that it isprovided with a rearwardlyprojecting flange 80, the follower member 'l'tisengaged and snaps the-spring fi'l'throug'h its over-centerposition. Insnapping through its over=eeriter position, the spring-'61 carries thefollowermember lt rearwardlybeyond the point where the 'flange-Bdengagesit. 'Itwill thus be observed that "there is no friction between thereel. 19 and the follower 16 during operating of the .unit.

Them-ashamed finger 1-! .is for the purpose-of resetting the deviceafter the reel 19 has been removed. "It will be observed that thisL-shaped finger 'klsha-srmoved outwardly through the opening :18 when:the bridging contact 65' moves to its: open "position. In order-toreset the devicethe outerend' of the L-shaped finger F! is depressed,which willagain' cause the spring 6 1 to'pass :throughitsover-centerposition to close thexabridging contact :65 against thecontacts .63- and-64.

Axvariation of this embodiment of the invention is shown in Figures 8and 9 of the drawings. More particularly, the switch units 34, 38 and 39(of which only unit 34 may be seen in the drawings) are the same type ofunit as the switch unit shown in Figure 7, with the exception that thisunit has been turned upside down. More particularly, the switch ismounted in such a position that when the L-shaped finger H is in theposition as shown in Figure 8 of the drawings, the switches 34, 38 and39 are open, while these same switches are closed when the L- shapedfinger I1 is in the position as shown in Figure 9 of the drawings. Inthis variation of the second embodiment of the invention, a spool orreel 8| is provided with an annular recess 82 in the back face thereofwhen the wire I4 wound thereon carries a recording of a permanentnature, and against which accidental erasure is to be prevented. Thisrecess 82 lies opposite the end of the follower 16 and when the reel BIis mounted does not in any way disturb the position of the follower 16.It will thus be seen that the switches 34, 38 and 39 will remain intheir open position under such circumstances. If, on the other hand, areel such as the reel 83 shown 7 in Figure 9, is mounted on the shaft60, it will strike the follower 16, force the spring 61 through itsover-center position and cause a closure of the switches 34, 38 and 39.

A third embodiment of the present invention is illustrated in Figures 10and 11 of the drawings. In this form of the invention the switch units34, 38 and 39 are of the same type as that described in connection withFigures 8 and 9. Instead of the arm 13 on the shaft H, however, anL-shaped arm 84 is provided. This arm 84 projects down through theopening 18 in the panel 62. When the arm is in its right-hand positionas shown in Figure 10 of the drawings, the switches 34, 38 and 39 are intheir. closed position, while the converse is true when the arm 84 is inits left-hand position. More particularly, when the arm 84 is in itsleft-hand position the switches 34, 38 and 39 are open. When a reel 83is mounted on the shaft 60, the outer peripheral flange of the reel willnot strike the finger 84. The switches 34, 38 and 39 will thus remain intheir closed position and the device may be used for either recording orreproducing. If, however, a reel 85 having a rear flange 86 of greaterdiameter than the front flange 81 is mounted on the shaft 60, the rearflange 86 will strike the finger 84 and rotate the shaft 1| to cause theswitches 34, 38 and 39 to open. A spool or reel of this character may beused to contain wire having a permanent recording thereon.

While I have shown particular embodiments of my invention, it will, ofcourse, be understood that I do not wish to be limited thereto, sincemany modifications may be made and I, therefore, contemplate by theappended claims, to cover all such modifications as may fall within thetrue spirit and scope of my invention.

I claim as my invention:

1. In a magnetic recording and reproducing device, a magnetic soundhead, electrically energized means for magnetically recording sound on awire, electrically energized means for reproducing sound previouslymagnetically recorded on a wire, said device being arranged to receiveand operatively mount wire carrying spools in operative relation withrespect to said head, switch means in the electrical energizing circuitof said recording means, said device having means thereon responsive tospools having a predetermined rim shape and dimension to open saidswitch means when such spools are mounted on said device.

2. A magnetic recording and reproducing device of the type whereinintelligence is recorded by varying the magnetic condition of a lengthymagnetizable medium along its length, said device including electricallyenergized elements to impart varying degrees of magnetization to saidmedium as it passes thereover to record intelligence thereon, a shaft toreceive a spool supporting said medium before it travels over saidelements during operation of said device, and a switch operable todeenergize said elements, said switch having an operating elementextending in direction parallel to the axis of said shaft to bearagainst an annular portion of the edge of said spool to control theenergization of said elements in accord with the axial extent of saidannular portion.

3. A a magnetic recording and reproducing device of the type whereinintelligence is recorded by varying the magnetic condition of a lengthyvmagnetizable medium along its length, said device includingelectrically energized elements to impart varying degrees ofmagnetization to said medium as it passes thereover to recordintelligence thereon, a shaft to receive a spool supporting said mediumbefore it travels over said elements during operation of said device,and a switch operable to deenergize said elements, said switch having anoperating lever extending in direction parallel to the axis of saidshaft and mounted for rotation relative to said axis to bear against theouter periphery of the end flange of said spool to control theenergization of said elements in accord with the diameter of saidflange.

HAROLD A. VAG'I'BORG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,560,721 OReilly Nov. 10, 1925,2,213,768 Merriman Sept. 3, 1940 2,321,812 Heller June 15, 19432,364,556 Somers Dec. 5, 1944

